'Toilet to Tap' Gains Appeal in Bone-Dry West

The idea, for many, may be too hard to swallow. But as California's historic drought drags on, experts and politicians are taking a serious look at "toilet to tap" options to guarantee long-term water supply.

The concept, which involves treating sewage water for human consumption, had until now failed to gain traction in the water-starved West Coast state largely due to the "yuck factor."

"Everyone is looking at wastewater recycling," said George Tchobanoglous, a water treatment expert and professor emeritus at the University of California, Davis.

"Right now, we discharge a lot of this treated wastewater into the ocean and we could certainly use it," he added. "And it's certainly feasible and cost effective in large metropolitan and coastal areas like California."

In a study published last year, Tchobanoglous estimated that by 2020, the concept known as potable reuse could yield more than 350 billion gallons per year, enough for more than eight million Californians, or roughly one-fifth of the state's projected population.

The technology is already being used successfully in several communities in Texas, which has also faced a severe drought.

There, in what is known as direct potable reuse (DPR) or "toilet to tap," wastewater from toilets, washing machines, dishwashers and showers is turned into drinking water following a three-step purification process.

A similar plan for the city of San Diego, in California, never got off the ground more than a decade ago because of stiff opposition.

But now, as the Golden State struggles to meet mandatory water restrictions and as options run out, the project is back on the table.

Tchobanoglous said recent polls conducted for San Diego's Water Authority found that support for wastewater reuse now stands at 76 percent, compared to 23 percent in the early 1990s.

Advocates of water reuse point to California's Orange County purification plant, one of the oldest and largest in the world, as an example of the environmental and financial benefits of the technology.

The plant, which opened in 2008 during a previous drought, recently underwent a $143 million expansion and treats 100 million gallons a day, enough for 850,000 people. A final expansion is planned to bring capacity to 130 million gallons a day.

"Traditionally sewer water was viewed as a waste but now we see it as a valuable resource from which we can produce one of the best quality waters," said Shivaji Deshmukh, assistant general manager at the West Basin plant.

Neither facility feeds its purified water directly into the drinking supply, as is the case in Texas.

Instead, it is infiltrated into the groundwater aquifer, which provides an environmental buffer, before it is drawn back to the surface for drinking.

But the technology is the same as that applied in direct potable reuse.

First the water goes through micro-filtration to get rid of tiny organisms such as bacteria. Then it is purified further through reverse osmosis. Thirdly, ultra violet light zaps any remaining particles.

The result is a water as pure, if not more, than that on supermarket shelves.

NASA uses the same technology on board the International Space Station, where special equipment recovers the crew's urine, breath vapor and sweat to produce water for coffee or brushing teeth.

The water reuse camp has a financial argument on its side, too. "Bottled water is typically 10,000 times more of the cost of tap water without necessarily being better quality wise," said Ron Wildermuth, spokesman at West Basin.

"About a day or two ago this water was sewage. Now it's the best quality water I could drink," he said, showing off a sample, and gulping it down.

Ongoing water shortages around the world, along with recent drought conditions in the western United States, have resulted in a flood of new research and proposals around water technology. We take a look at some concepts -- from simple to complex to rather ancient -- that are designed to help us collect, store, transport and even create water where it's needed most.

The severe drought in California -- now in its third year -- has triggered new interest in a relatively old technology. Desalination plants turn seawater into drinking water by way of high pressure valves and semi-permeable membranes. Traditionally an expensive and energy-intensive process, recent innovations have made desalination a more viable option. The city of Carlsbad, Calif., is set to open the biggest

(HCPVT) system, designed to generate solar power and desalinate water at the same time. The sunflower-shaped solar collectors use a liquid cooling system that could potentially double as a small-scale desalination plant, providing both energy and water for apartment buildings, hotels or hospitals.

Water recycling is the umbrella term for reuse and reclamation systems that involve treating wastewater and returning it to underground aquifers or reservoirs. Along with desalination, it's among the existing technologies being optimized for large-scale use. San Diego's

water-harvesting billboard in Lima, Peru, uses dehumidifiers to pull moisture out of the atmosphere. Then a drip irrigation system waters the adjacent garden, producing more than 2.500 heads of lettuce per week. The billboard was built by -- and advertises -- Lima's University of Engineering and Technology.

Lima is the kind of town that doesn't mess around. As the second largest desert city in the world (behind Cairo), it has faced water problems for centuries. A new initiative by the city's water utility plans to

. A few years back, German design student Imke Hoehler proposed a design for portable and collapsible tent-like fog nets that could potentially harvest up to 20 liters of water per day under the right conditions.

In March, a team of Japanese scientists proposed studying the microscopic workings of certain moisture-gathering plants to design the next generation of water collection systems. Electron microscope imagery reveals that such plants use cone shaped hairs to catch and store water, then change shape release the moisture in dry conditions. The team hopes advanced fiber technology could essentially replicate the process.

Designed and built by the Washington-based engineering firm, Janicki Bioenergy, the very official-sounding Omniprocessor S100 uses heat from sludge to make water. A trial run is underway in Dakar, Senegal, where the machine -- which has received funding from the Bill and Melinda Gates Foundation -- is processing sewage from a community of about 100,000 people. The sewage is first heated intensely to dry it and then during the process, the water vapor is captured, heavily processed and turned into drinking water.